Traffic Information Providing System and Car Navigation System

ABSTRACT

A traffic information providing system externally acquires traffic information including information relating to the travel time of a link, calculates a travel time for a non-provision link to which no travel time is provided through estimate/complement operation. The estimate/complement operation is carried out with use of travel times, emergencies, travel times of links in the vicinity of the non-provision link, and so on, obtained in the near past. The system stores and statistically processes the externally-acquired traffic information, and also estimates a travel time in the near future. When there is an abnormality in the acquired traffic information, the system deletes the abnormality, regards the information as a non-provision link, calculates a probability distribution of travel times of links, calculates a probability distribution of travel times of the entire route made up of a plurality of links, and also calculates a probability for a specific travel time range.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a divisional application of U.S. patentapplication Ser. No. 12/027,433, filed Feb. 7, 2008, which is adivisional application of U.S. patent application Ser. No. 10/932,061,filed Sep. 2, 2004, which claims priority to Japanese patent applicationno. JP 2003-356500 filed Oct. 16, 2003, and Japanese patent applicationno. JP 2003-361385, filed Oct. 22, 2003, the disclosures of each ofwhich are incorporated by reference herein in their entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a car navigation system and moreparticular, to a technique of processing traffic information such astraffic jam or travel time and a technique of receiving and outputtingprocessed traffic information in a system for performing communicationbetween a car terminal and a server.

2. Description of the Related Art

There are disclosed systems in which when start and end points aretransmitted from a car terminal to a server, the server searches for aroute, searches for traffic information, and then returning both of theroute and the traffic information to the terminal, in JP-A-2001-356021and JP-A-2001-289656. In these systems, all the traffic informationexisting on the route are searched for and returned to the terminal.

Such a technique for estimating a travel time based on other informationwith respect to a link having no information about travel time astraffic information (which will be referred to as non-provision link,hereinafter) as disclosed in JP-A-7-129893, is known. In the technique,the average vehicle speed of the link is calculated based on traffic jamor congestion information included in external information. And thecomplementary information for the non-provision link is calculated basedon the calculated average vehicle speed. The travel time of the link isalso estimated based on the average vehicle speeds of individual timezones for each of previously stored links.

Such a technique for finding a reliability in the predicted value of therun time as disclosed in JP-A-2002-260142, is known. In the technique,data about run times of a road section including the road in questionuntil the current time are collected, a run time memory table having runtime data past collected is searched for one of patterns similar in therun time, and a run time memory value for the pattern is used as apredicted run time ahead of N hours. By repeating such operations, aplurality of candidates of the predicted run time are found, mostfrequent one of the candidates is determined as the predicted run time,and the reliability of the predicted run time is found on the basis of aspread in the distribution of the candidates.

The technique disclosed in JP-A-7-129893 is intended to be applied to avehicle route guiding system. However, traffic information is updatedfrom moment to moment, and when traffic information past received arealso included in the first-mentioned traffic information, a memorycapacity and a processing quantity correspondingly become enormous. Insuch a vehicle route guiding system as not enough in the memory capacityand processing performance, generally speaking, it is difficult for thesystem to estimate a travel time of a non-provision link on a real timebasis. In addition, it is also inefficient for individual vehicle routeguiding systems to perform the same operations.

The technique disclosed in JP-A-2002-260142 has a problem from aviewpoint of convenience. For example, even when a prediction error Wswithin a probability S is found, the error Ws may fail to fall in apractical range. For example, the prediction error Ws within 90% of aprobability S for a predicted run time value of 20 minutes becomes 100minutes or so.

SUMMARY OF THE INVENTION

In view of the above circumstances, it is therefore an object of thepresent invention is to enable processing of traffic information withoutimposing a burden on a device carried on a car or the like. A relatedobject of the present invention is to provide accurate trafficinformation and its reliability information with respect to many linksincluding a non-provision link, by integrally suitably processingtraffic information such as VICS (Vehicle Information CommunicationSystem) traffic information that is not so high in reliability andstability.

In the above related art, it may occur such a situation that the longera route is the larger the quantity of data about traffic information isproportionally, thus prolonging a communication time. A communicationfee imposed on the user also becomes correspondingly high. Further, withrespect to traffic information at a position so much away from thecurrent location, the traffic information when searched for may becomesdifferent from the traffic information when the car arrived at thatposition. In other words, even when all the traffic information on aroute have been downloaded in a route search mode, only part of thedownloaded traffic information in the vicinity of the own vehicle can beactually used effectively, and even when traffic information at aposition too much away therefrom is obtained, the information is notalways used effectively.

Another object of the present invention is to lighten a user'scommunication fee burden and to distribute traffic information seeminglymore effective at that time point, by reducing a communication time anda quantity of communication information in acquiring traffic informationon a route.

The traffic information providing system in accordance with the presentinvention creates traffic information to be used in the car navigationsystem. The traffic information providing system includes a trafficinformation acquiring means for externally acquiring traffic informationincluding information about a travel time for each link forming a roadon a map, and a complementing means for calculating traffic informationon the travel time by estimating and complementing a non-provision linkto which information on the travel time is not provided.

In this connection, the traffic information providing system may includea storage means for storing the traffic information acquired by thetraffic information acquiring means and a statistical means forstatistically processing past traffic information so far stored by thestorage means.

The traffic information providing system of the present invention alsoincludes a traffic information acquiring means for externally acquiringtraffic information including information about a travel time for eachlink forming a road on a map, and an abnormal value deciding means fordeciding abnormal data in the traffic information acquired by thetraffic information acquiring means. The abnormal value deciding meanshas at least one of a function of deciding that data having a congestionfrequency of a predetermined value or more is abnormal, a function ofdeciding that traffic information having a deviation larger than trafficinformation corresponding to a plurality of days in an identical timezone is abnormal, and a function of comparing a travel time andcongestion information and deciding that the congestion information isabnormal when one of the travel time and congestion information variesin a normal range but when the other indicates a constant values.

The traffic information providing system of the present invention alsoincludes a traffic information acquiring means for externally acquiringtraffic information including information about a travel time for eachlink forming a road on a map, and the traffic information acquiringmeans has a storage means for storing the acquired traffic information.The traffic information providing system also includes a linktravel-time probability calculating means for calculating a probabilitydistribution relating to a travel time for each link, a route trip-timeprobability calculating means for calculating a probability distributionrelating to travel times of a specific route formed by a plurality oflinks with use of the probability distribution of the travel time of thelink calculated by the link travel-time probability calculating means,and a means for calculating a probability of the travel time of thespecific route calculated by the route trip-time probability calculatingmeans.

The car navigation system of the present invention includes a means foracquiring information created by the traffic information providingsystem and relating to a probability distribution of travel time foreach link; a route trip-time probability calculating means forcalculating a probability distribution of the travel time of a specificroute made up of a plurality of links with use of the probabilitydistribution of travel time of each link; a setting means for setting atravel time range or a travel time probability for the specific route; areliability calculating means for calculating a probability that thetravel time of the specific route is in the travel time range set by thesetting means with use of the probability distribution of the trip timeof the specific route, and when the travel time probability of thespecific route is set by the setting means, for calculating such atravel time range that the travel time of the specific route falls inthe travel time probability set by the setting means with use of theprobability distribution of the travel time of the specific route; and areliability display means for displaying a result calculated by thereliability calculating means.

Another terminal in the present invention is provided with a positionmeasuring means for measuring the position of own terminal, a targetposition setting means for setting target position information, acommunication means for transmitting and receiving data to and from aninformation center, a route guiding means for guiding the car along aroute to the target position, and a traffic information acquiring meansfor acquiring traffic information at least on the route or relating tothe vicinity of the route. And the terminal also has a means forspecifying a traffic information acquirement range. When issuing atraffic information acquirement request to the information center, theterminal uploads the specified acquirement range to the informationcenter.

The terminal has a display screen as a means for the user to specify andenter the traffic information acquirement range. The terminal also haspreviously a default value within the traffic information acquirementrange, and the default value is also displayed on the screen. And theterminal uploads its status to the information center, and theinformation center decides the traffic information acquirement rangeaccording to the uploaded status of the terminal.

When issuing a traffic information acquirement request to theinformation center, the terminal uploads the route information held bythe terminal to the information center. The information center transmitsor received data to or from the terminal, and holds it as an extractionrange of the uploaded traffic information on the route or relating tothe vicinity of the route. The information center, when receiving therequest from the terminal to acquire the traffic information on theroute or relating to the vicinity of the route, also receives the statusof the terminal and decides the traffic information extraction range.The information center already the default value of the trafficinformation extraction range, receives a parameter indicative of thetraffic information extraction range from the terminal, and extracts thetraffic information.

For the traffic information acquisition/extraction range; at least oneof a specific or all sections on the route, a section through which thecar passes in a certain time, a section away by a constant distance fromthe position of own car or for which the size of the information isequal to or smaller than a constant value, all non-passage routes, and asection between two points on the route; is specified.

During connection to the information center and downloading of thetarget information, if emergency information is held in the informationcenter, then the terminal downloads the emergency information togetherand displays it. When the emergency information is included in thedownloaded information, the terminal displays the emergency informationpreferentially to the initial target information.

In accordance with the present invention, since traffic information isprocessed by the traffic information providing system, a processingburden imposed on the car navigation system mounted on the car or thelike can be lightened.

In accordance with the present invention, further, since a trafficinformation reception range is specified, the communication time or thequantity of communication information can be reduced, user'scommunication fee burden can be lightened, and traffic informationseemingly most effective at that time points can be provided.

Other objects, features and advantages of the invention will becomeapparent from the following description of the embodiments of theinvention taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an example of an arrangement of a traffic informationproviding system;

FIG. 2 shows how stored traffic information database DB manages trafficinformation;

FIG. 3 is a flowchart showing a flow of operations for creating trafficinformation on a real time basis;

FIG. 4 shows a flow of complementing operations;

FIG. 5 is a diagram for explaining the complementing operation of anunknown section of a link relating to a degree of congestion;

FIG. 6 is a road network for explaining how to complement the traveltime of a non-provision link using the travel time of a peripheral link;

FIG. 7 is a flowchart showing a flow of operations of creating astatistical travel time;

FIG. 8 shows an example of a probability distribution relating to a linktravel time;

FIG. 9 is a road network for explaining an example of how to utilize thelink travel time;

FIG. 10A shows a statistical travel time for each link and time zone forexplaining how to predict a route travel time;

FIG. 10B shows a statistical travel speed for each link and time zone;

FIG. 11 shows a running status in the course of a route as an example ofexplaining how to predict a route travel time;

FIG. 12 is a diagram for explaining how to find a probability of theroute travel time according to a probability dense function;

FIG. 13 is a flowchart showing a flow of operations of displaying aprobability and so on relating to the route travel time on a userterminal;

FIG. 14 shows an example of a screen for displaying and setting a traveltime;

FIG. 15A shows an example of a screen for a travel time and aprobability;

FIG. 15B shows an example of a screen for a travel time and aprobability;

FIG. 15C shows an example of a screen for a travel time and aprobability;

FIG. 16 shows a general system in accordance with another embodiment ofthe present invention;

FIG. 17 shows a structure of a navigation server 1602;

FIG. 18 is a communication sequence chart between a car terminal 1606and the navigation server 1602;

FIG. 19 is a sequence chart when on-route traffic information isdownloaded;

FIG. 20 is a flowchart showing the on-route traffic informationextracting operation of the traffic information server 1702;

FIG. 21 is a flowchart showing the on-route traffic informationdisplaying operation of the car terminal 1606;

FIG. 22 shows an example of a screen on which a main menu is displayed;

FIG. 23A shows an example of a screen on which an emergency message isdisplayed;

FIG. 23B shows an example of a screen on which traffic information otherthan the emergency is displayed;

FIG. 24 is a sequence chart when traffic information about the vicinityof the position of the car is downloaded;

FIG. 25 shows an example of a screen on which traffic information isdisplayed;

FIG. 26 is a sequence chart when the car terminal 1606 requests thenavigation server 1602 to issue map information to the car terminal;

FIG. 27 shows a screen on which an emergency message is displayed; and

FIG. 28 shows a configuration of modules in a navigation application.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Explanation will be made in connection of an embodiment of the presentinvention with reference to the accompanying drawings. FIG. 1schematically shows a traffic information system to which an embodimentof the present invention is applied. The traffic information system auser terminal 200, a communication network 103, a traffic informationproviding system 107, a traffic information providing center 100 forproviding information such as a VICS center. The user terminal 200 hascommunication network interface (IF) 201, an information processor 202,a user IF 203, a storage 204, and a display 205. The informationprocessor 202 receives various sorts of traffic information from thetraffic information providing system 107 via the communication networkIF 201 and communication network 103, and stores the received trafficinformation in the storage 204. The information processor also accepts auser's request via the user IF 203, suitably processes the trafficinformation according to the contents of the request, and displays it onthe display 205. In this connection, the user terminal 200 is notnecessarily required to be mounted on a vehicle.

The traffic information providing system 107 has a communication networkIF 112, a user management unit 113, a route searching unit 114, a mapdatabase (DB) 126, and a traffic information management unit 116. Thecommunication network IF 112 supports communication mediation betweeneach unit of the traffic information providing system 107 and the userterminal 200 via the communication network 103. For example, when thecommunication network 103 is the WWW (World Wide Web) or Internet, CGI(Common Gate Interface) can be used as the communication network IF 112.The user management unit 113 registers and edits user information. Theroute searching unit 114 calculates a route from the position of the carto a target position according to a route searching technique such asthe Dijkstra algorithm using map data and so on on the basis ofinformation about a departure position (current position) and a targetposition or on the basis of information about the departure (current)position, the target position and a passing-through position, sent fromthe user. In this connection, when the user terminal has a routesearching function, provision of the route searching unit 114 in thetraffic information providing system 107 is not indispensable.

Registered and managed in the map DB 126 for each of mesh regionsobtained by dividing a map into a plurality of regions are data aboutthe identification codes (mesh IDs) of the mesh regions and about linksforming roads included in the mesh region. The link data includes a linkidentification code (link ID), coordinate information of two nodes(start and end nodes) forming a link, attribute information on nationalor prefectural roads, information indicative of restricted speed, linklength/width, information on the trip speed for each congestion degree,and the IDs (connection link IDs) of links connected to the two nodes.Also included in the map data are information on main intersections andinformation (such as title, type and coordinate information) about mapstructures other than roads included in the corresponding mesh region.

The traffic information management unit 116 has a traffic informationreceiver 130, a stored traffic information DB 180, a traffic informationprocessor 132, a processed traffic information DB 133, and adistribution information generator 137. The traffic information receiver130 receives traffic information including traffic, congestion, traveltime, restriction/fault information, information on empty or fullparking lot, and intersection signal information, periodically sent fromthe traffic information providing center 100. The stored trafficinformation DB 180 registers and manages various sorts of trafficinformation received from the traffic information receiver 130. FIG. 2shows an example of traffic information to be registered and managed bythe stored traffic information DB 180. The stored traffic information DB180 manages the traffic information on each collection date(registration date) 1821. The DB also manages the traffic informationfor each link ID 1822. The traffic information includes information 1824about link travel time (travel speed) and information 1825 aboutcongestion such as congestion degree and congestion length. The storedtraffic information DB 180 also manages information about the type 1826of a day corresponding to the collection date 1821. The day type isclassified by weekday and holiday, by weekday, or by action patterns ofcommon or general users. In the latter action classification case, forexample, the day type may be classified by the consecution of weekdaysor holidays, e.g., by the first, middle and last days in the consecutiveweekdays or by the first, middle and last days in the consecutiveholidays. Weather may be considered to be added to the aboveclassification.

The traffic information processor 132 deletes an abnormal value(singular value) in the stored traffic information DB 180, and suitableprocesses (complementes or statistically processes) a link having noinformation, detailed processing operations of which will be explainedlater.

The processed traffic information DB 133 manages various sorts oftraffic information created or generated by the traffic informationprocessor 132. The processed traffic information DB 133 has a real-timetraffic information DB 135, a statistical traffic information DB 134 anda predicted traffic information DB 136 for storing traffic informationrelating to future traffic statuses. The real-time traffic informationDB 135 manages the current traffic information for each link. Thestatistical traffic information DB 134 manages the traffic informationgenerated through the statistical processing for each day type, eachlink and each time (time zone). The predicted traffic information DB 136manages future traffic information for each day type, each link and eachtime (time zone).

The distribution information generator 137, in response to a requestfrom the user terminal 200, converts or molds the information of theprocessed traffic information DB 133 to information having apredetermined format, generates distribution information, and returnsthe generated information to the user terminal.

Explanation will next be made as to how the traffic informationprocessor 132 generates processed traffic information. First how togenerate real-time traffic information will be explained according to aflowchart of FIG. 3. When generating the real-time traffic information,the traffic information processor 132 first refers to the collectiondate 1821 and reads the latest traffic information (step S1100). Next,the traffic information processor 132 decides whether or not the readtraffic information is abnormal (singular) (step S1101). For example,when a link travel time corresponding to a high speed largely exceedinga restricted speed is included in the information or when a link traveltime not smaller than a predetermined value or a link travel timecorresponding to a too slow speed not exceeding the predetermined speedis included in the information, the traffic information processordetermines that the read traffic information is abnormal. Or whenconsistency is not provided between the link travel time and thecongestion information, as when the link travel time is differentlargely from a travel time obtained by converting the congestion degreeto a speed, the both traffic information may be decided as abnormal.When deciding the information as abnormal, the traffic informationprocessor 132 deletes the traffic information decided as abnormal fromthe stored traffic information DB 180 not to be used in the subsequentoperations (step S1102). The operations of the steps S1101 and S1102 arecarried out for traffic information of all links of the latest trafficinformation managed by the stored traffic information DB 180 (stepS1103).

Next, the traffic information processor 132 decides whether or notsignificant travel time information is provided to each link (stepS1104). In this connection, the word “significant travel timeinformation” as used herein refers to travel time information notdecided as abnormal through the abnormal value decision and stillremaining in the stored traffic information DB 180. And a link(non-provision link), to which the significant travel time informationis not provided, is subjected to estimate/complement operation (detailsof which will be explained later) (step S1105). The operations of thesteps S1104 and S1105 are carried out for all the links (step S1107).Through the above operations, real-time traffic information isgenerated. And the traffic information processor 132 stores thegenerated real-time traffic information in the real-time trafficinformation DB 135. When the above operations are executed at intervalswhen traffic information is newly registered by the traffic informationproviding center 100, the latest real-time traffic information can beheld.

Explanation will now be made as to the estimate/complement operationS1105. Even when there is no significant link travel time information ina link to be subjected to be estimated and complemented, the travel timeof the non-provision link can be estimated, complemented and calculatedon the basis of other available traffic information (alternative trafficinformation). Explanation will be made as to the estimate/complementoperation, by referring to a flowchart of FIG. 4.

(a) The traffic information processor 132 first decides whether or not atravel time for a non-provision link is included in past trafficinformation (step S1500). When a travel time for a non-provision link isincluded (YES in the step S1500), the traffic information processor 132refers to the information collection date 1821, and applies one of thepast link travel times most close to the current time as the travel timeof the non-provision link (step S1503). However, if a significant traveltime information can be obtained only when the most-close link traveltime is dated older by a predetermined time (e.g., 1 hour) or more thanthe current time, the past link travel time is not applied. When aplurality of significant travel times are present by going back to apredetermined time, the significant travel times are weighted in anearlier order of time, and an average value thereof may be applied.

(b) When a travel time for a non-provision link is not included in thepast traffic information (NO in the step S1500), the traffic informationprocessor 132 decides whether or not congestion information is includedin the traffic information of the non-provision link (step S1501). Ifthe congestion information is included (YES in the step S1501), then thetraffic information processor 132 calculates the link travel time on thebasis of the congestion degree and congestion length of thenon-provision link with use of a travel time (moving speed)corresponding to each congestion degree for each predetermined road type(step S1504). At this time, if a section having an unknown congestiondegree is present in the non-provision link, then the congestion degreeof the unknown congestion-degree section is regarded as normal. When acongestion degree (congestion length 401 of 300 m, heavy-traffic length402 of 200 m, normal length 403 of 250 m) in an identical link 400 isknown as shown in FIG. 5, the traffic information processor 132 firstfinds a length rate for the congestion degree. And a congestion lengthfor each congestion degree is found by multiplying the length rate ofeach congestion degree by the length of a unknown congestion-degreesection 404. In FIG. 5, when a unknown congestion-degree section (250 m)is applied to each length, the congestion length is 100 m, theheavy-traffic length is 67 m, and the normal length is 83 m. Through theabove operations, a congestion degree and its length are found for theunknown congestion-degree section and thus a travel time for anon-provision link can be calculated.

(c) When congestion information is not included in the trafficinformation of the non-provision link (NO in the step S1501), thetraffic information processor 132 decides whether or not a significanttravel time is included in the traffic information of links in thevicinity of the non-provision link (e.g., within a predetermineddistance of 2 km) (step S1502). If the significant travel time isincluded (YES in the step S 1502), then the traffic informationprocessor 132 selects specific one from the links in the vicinity of thenon-provision link, and calculates a travel time for the non-provisionlink from the travel time of the selected link (step S1505). Now, fromthe viewpoint of estimation accuracy, it becomes important which link isselected. To this end, how to select the link will be explained with useof an exemplary virtual road network of FIG. 6. In the drawing, R1denotes a national road No. 1, Pref. 1 (Pref. R1) denotes a prefecturalroad No. 1, City 1 (City R1) denotes a city road No. 1, and so on.Arrows 410 to 418 and 420 to 427 given along the national road No. 1 andthe prefectural road No. 1 indicate the presence or absence ofsignificant travel time information. More specifically the solid-linearrows 410 to 418 mean links having significant travel time informationpresent therein; whereas, the dashed-line arrows 420 to 427 means linkshaving significant travel time information not present therein. In thisexample, with regard to the dashed-line arrows 420 to 427, explanationwill be made as to how the traffic information processor 132 selectssuitable one from peripheral links having significant travel timeinformation.

The traffic information processor 132 first (i) selects ones of links inthe vicinity of the non-provision link which belongs to the same road(e.g., national road No. 1) as the non-provision link. The trafficinformation processor 132 (ii) selects one of the selected links whichspans the main intersections 430 to 433 during connection with thenon-provision link a smallest number of times. The main intersection maybe an intersection whose traffic condition largely varies, e.g., whichforms a change point such as a congestion bottleneck in the trafficcondition, or be an intersection where main roads such as prefecturaland national roads and an expressway cross each other. At this time,priorities may be applied to the main intersections 430 to 433 in anascending order of straddling frequency to select a plurality of links.When the link section is not done in Paragraph (i), the trafficinformation processor 132 performs the link selection of Paragraph (ii)for all links in the vicinity of the non-provision link. The trafficinformation processor 132 next select one of the selected links whichhas a smallest distance from the non-provision link. However, when alink is directly connected to the non-provision link or has a smallestdistance therefrom but when the link is located on the opposite side(opposite car lane) to the non-provision link, the traffic informationprocessor 132 does not select the link. In this case, priorities may beapplied to links in an increasing order of distance from thenon-provision link to select a plurality of links. Whether to be anidentical road, whether to be a main intersection, or whether or not thelink is directly connected can be decided by examining link data andintersection information in the map data. When priorities are applied tolinks to select a plurality of links, the traffic information of theselected links are weighted in the priority order and averaged to beused for calculation of the travel time of the target link.

According to the link selection method mentioned above, a link 411 isselected most preferentially in order to complement and estimate atravel time for a link 420 in FIG. 6. A link 410 is next selected. For alink 421, a link 412 is selected most preferentially. For a link 422, alink 413 is selected most preferentially. For links 423 and 425, links414 and 415 are selected with the same priority. In this case, anaverage value of traffic information of the both links is used tocalculate a travel time for the link 423. Similarly, for a link 424, alink 416 is selected most preferentially, and for links 426 and 427, alink 417 is selected most preferentially. In this manner, the trafficinformation processor 132 suitably selects links in the vicinity of thenon-provision link and calculates a travel time for the non-provisionlink using the travel times of the selected links.

(d) When a link having a significant travel time information is notpresent in the vicinity of the non-provision link (NO in the stepS1502), the traffic information processor 132 extracts links having thesame road attributes (mesh, road, road type, direction, etc.) as thenon-provision link (e.g., the same national road) from the map DB 126.For the extracted links, the traffic information processor 132 searchesthe stored traffic information DB 180 for their travel times and findsan average travel speed therefrom. The traffic information processorfinds a travel time for the non-provision link from the average travelspeed and the link length of the non-provision link (step S1506).

Explanation will then be made as to how to generate statistical trafficinformation according to a flowchart of FIG. 7. The traffic informationprocessor 132 first reads out traffic information in a specified period(e.g., about weekdays in past half year) from traffic information storedin the stored traffic information DB 180, by referring to theinformation collection date 1821 and the day type 1826 (step S1200). Inthe aforementioned creating operation of real-time traffic information,it is only required to read out the latest traffic information. In thecreating operation of statistical traffic information, however, thetraffic information processor 132 reads out traffic informationcorresponding to a plurality of times of a plurality of days(corresponding to a full 24-hour time zone) to be processed. Thespecified period is previously set according to applications of thestatistical traffic information or the like.

The traffic information processor 132 then decides whether or not theread-out traffic information is abnormal (singular) for each link (stepS1201). Similarly to the above method for generating real-time trafficinformation, such an abnormal value deciding method can be employed thatthe traffic information processor decides it as abnormal when linktravel time having a too high or slow speed is included in the trafficinformation or when inconsistency is detected between the congestiondegree and the travel time. The presence or absence of an abnormalitymay be decided by comparing the traffic information with trafficinformation of another day having the same day type 1826. Morespecifically, the abnormal value deciding method includes a methodwherein, when a congestion time (rate) in one day exceeds apredetermined value (e.g. 5 hours), traffic information corresponding tothe full day are decided as abnormal; and a method wherein, when one ofthe traffic information corresponding to a plurality of days in anidentical time zone has a value largely different from the values of theother information (has a remarkably large deviation), the trafficinformation is decided as abnormal.

The traffic information processor 132 deletes the traffic informationdecided as abnormal from the stored traffic information DB 180 and doesnot use it in the subsequent processing (step S1202). The operations ofthe steps S1201 and S1202 are applied all the traffic information oflinks in the specified period (step S1203).

Next, on the basis of traffic information not deleted through theabnormal information deleting operation (step S1202), the trafficinformation processor 132 statically processes the traffic information,and creates statistical traffic information such as travel time (travelspeed) and congestion degree for each day type, each link an each time(time zone). At this time, the traffic information processor 132 finds aprobability distribution (probability dense function 440) relating tolink travel time as shown in FIG. 8 for each day type, each link andeach time (time zone) (step S1206).

The traffic information processor 132 next refers to the createdstatistical traffic information, and decides whether or not significanttravel time information is provided for each link (step S1204). And withrespect to the non-provision link to which significant travel timeinformation is not provided, the traffic information processor,similarly to the real-time traffic-information creating operation,estimates and complements a travel time from the traffic information,etc. of the other links, and adds the obtained traffic information tothe statistical traffic information (step S1205). Theestimate/complement method can be carried out similarly to theestimate/complement operation in the real-time traffic-informationcreating operation. When calculating a travel time with respect to atime (target time) at which the link travel time is not provided, thetraffic information processor examines whether or not a time (time zone)during which the link travel time is provided is present in apredetermined time range (e.g., 5 hours) before and after the targettime. When the link travel time is provided, the link travel time isemployed as a travel time for the target time. The predetermined timerange is previously set to a time range in which the traffic conditionwill be seemed not to vary largely. The operations of the steps S1204 toS1206 are carried out for all times (step S1208). As a result, traveltimes for all times (time zones) of the link can be found. Further, theoperations of the steps S1204 to S1208 are carried out for all links(step S1209). As a result, statistical traffic information in a widearea is complemented. When such a processing flow is executed atpredetermined timing, e.g., at intervals of one month, season or oneyear; statistical traffic information can be stably provided withoutlowering the freshness of information.

Explanation will then be made as to how to create predicted trafficinformation. When creating predicted traffic information with regard toa specific link (target link), the traffic information processor firstread out a travel time Td′(t) of the latest target link at a currenttime t from the real-time traffic information DB 135. The trafficinformation processor then searches the predicted traffic information DB136 for a travel time Td(t) of the target link at the current time t andfor a travel time Td(t+n) to be predicted at a near future time (t+n)after passage of a predetermine time. And the traffic informationprocessor multiplies the travel time Td(t+n) by [travel timeTd′(t)/travel time Td(t)] to obtain a predicted travel time Td′(t+n) ofthe target link at the time (t+n). When the above operations are carriedout for each link, the predicted traffic information DB 136 havingfuture data in a wide area can be formed. When the traffic informationprocessor executes the above processing flow at intervals of a time(usually, 5 minutes) updated by the traffic information providing center100, the processor can quickly and efficiently provide predicted trafficinformation to the user.

Explanation will next be made as to an example of calculating a traveltime for a specific route made up of a plurality of links with use oflink travel times (significant travel times) stored in the statisticaltraffic information DB 134. As an example of a simple road network, FIG.9 is considered. In the drawing, A to E denote intersections, and 460 to463 denote links. It is assumed that link lengths of the links 460 to463 as well as significant travel times and statistical travel speedsfor each time zone are as shown in FIGS. 10A and 10B. In the drawings,“10:00” means significant travel times or statistical travel speeds attime points included in a time period starting at 10:00 and ending at10:05 (not included). The statistical travel speed is found from thesignificant travel time and the link length for each time zone.Explanation will be made as to how to calculate a significant traveltime between the intersections A and E. When the car starts at a time10:00:00 from the intersection A, it is estimated that it takes 72seconds (30 km/h in average speed) for the car to pass through the link460. Since a time point 10:01:12 at which the car will probably arriveat the link 461 does not reach 10:05 yet, the traffic informationprocessor selects “25 km/h” in the column “10:00” as a predicted travelspeed of the next link 461. For this reason, a travel time necessary forpassage of the car through the link 461 is 144 seconds, and a totaltravel time from the intersection A is 216 seconds. Similarly, a traveltime necessary for passage through the link 462 is calculated to be 82seconds (298 seconds in total time). Since a travel time necessary forpassage through the last link 463 is 173 seconds (471 seconds in totaltime), it is required to change the speed for “10:05” on the way. Thatis, since the speed “10:00” (25 km/h) is selected for first 2 secondsafter the car enters the link 463, a run distance is about 14 m duringthe first time. And a speed “10:05” (15 km/h) is selected for theremaining distance of 1186 m. Thus it takes about 285 seconds for thecar to pass through the remaining part of the link. As a result, atravel time necessary for passage through the link 463 is calculated tobe 287 seconds (585 seconds in total time). From the aboveconsideration, it is estimated that the car departing from theintersection A at 10:00:00 will arrive at the intersection E at a time“10:09:45”, and thus the car running status of the entire route is asshown by a graph 464 in FIG. 11. Similarly, the running status of thecar departing from the intersection A at a time “10:05:00” is as shownby a graph 465 in FIG. 11, a significant travel time until theintersection E is calculated to be 759 seconds, and an estimated arrivaltime is to be “10:17:39”.

Explanation will then be made in connection with an example ofcalculating a probability distribution of travel time of a specificroute including a plurality of links as a application example of theprobability distribution. Explanation will be made, in particular, as tohow to find a probability distribution of travel time of a route AE fromthe intersection A to the intersection E in the road network of FIG. 9.As in the above case, the traffic information processor can know aprobability distribution of time points in each link considering thetime passage of the car running with a departure time from theintersection A as a start point, by referring to the statistical trafficinformation DB 134. A probability f for travel times X1, X2, X3 and X4of the links 460, 461, 462, and 463 is f460(X1), f461(X2), f462(X3), andf463(X4) respectively. The probability f can take various valuesaccording to the X1, X2, X3, and X4 as shown in FIG. 8. Assuming nowthat probability distributions of link travel times are independent ofeach other, then a probability f(X) that the travel times of the links460, 461, 462, and 463 are x1, x2, x3, and x4 respectively (the traveltime X of the route AE being x1+x2+x3+x4), is expressed by an equationwhich follows.

f(X)=f460(x1)·f461(x2)·f462(x3)·f463(x4)  (1)

When the traffic information processor calculates possible combinationsof all the X1, X2, X3, and X4 and adds them together for the same X, theprocessor can obtain a probability dense function f(X) with respect to atravel time X for the route AE. And the traffic information processorcan find an expected value E for the travel time of the route AE, adeviation σ, etc using the probability dense function f(X). When such aprobability dense function 470 as shown in FIG. 12 is used, further, thetraffic information processor can find a probability that the traveltime X is include in a range of E±ΔX as a ratio of the area of a hatchedarea 471 to an area surrounded by the probability dense function 470 andits X axis line. By changing ΔX (difference from E), the trafficinformation processor can find a probability P (ΔX) of various range oftravel times.

The application example of link travel time or the application exampleof the probability distribution of travel time has been explained above.However, the operations involved by these examples may be carried out bythe traffic information providing system 107 or by the user terminal200.

Explanation will then be made as to an example when an average traveltime E, a travel time range E±AX for a specific route (target route),and a probability P(ΔX) of the travel time range are displayed on theuser terminal 200, by using a flowchart of FIG. 13.

The information processor 202 first sets various values associated withthe display of the travel time (step S1400). The various set valuesinclude a travel time range and a travel time probability (correspondingto the probability P of travel time range). The travel time range may befound and set by accepting selection of a travel time width(corresponding to twice the ΔX) indicative of the display width of thetravel time and finding them according to the equation of travel timerange E±ΔX. At this time, the information processor 202 displays on thescreen 140 of the display 205 a radio button 480 to select one of thetravel time width and the travel time probability is preferentiallydisplayed as an index. Reference numerals 481 to 483 in the screen 140denote candidate buttons for set values of setting items.

Next, the information processor 202 issues a request to the trafficinformation providing system 107 to cause the system to calculate atravel time (average travel time) for the target route, a probabilitydistribution thereof, an expected value thereof, and a travel timeprobability for the set travel time range. The traffic informationproviding system 107 calculates these values according to theaforementioned method, and then transmits them to the informationprocessor 202 of the user terminal 200 (step S1401). In this connection,the information processor 202 itself may calculate these values. Theinformation processor 202 then decides whether or not a calculatedresult satisfies predetermined conditions (step S1402). The conditionsare set as the maximum width (e.g., 60 minutes) of the travel time widthand the lower limit value (e.g., 40%) of the travel time probability.When the set values exceed these conditions, this means that theinformation has a low reliability.

As a first example, when an average travel time of 45 minutes, a traveltime range of 40-50 minutes, and a travel time probability of as highlylow as 20% are calculated for the travel time width of 10 minutes, thelower limit (e.g., 40%) of the travel time probability fails to satisfythe above conditions. As a second example, when an average travel timeof 55 minutes, a travel time probability of 90%, and a travel time rangeas highly wide as 10-100 minutes are calculated for the travel timeprobability set at 90%, the travel time width exceeds the maximum width(e.g., 60 minutes) of the travel time width, and thus the conditions arenot satisfied. As a third example, even when the travel time width isset at 30 minutes, if the value of the average travel time becomes 10minutes, then the travel time range becomes −5 minutes to 25 minutes.That is, the minimum value may be calculated as a value of zero orlower. Even in this case, the conditions are not satisfied. Similarly,even when the maximum value of the travel time range exceeds apredetermined value (e.g., 10 hours), the conditions are not satisfied.As in the above, when the conditions are not satisfied, the informationprocessor 202 automatically modifies the travel time width or the traveltime probability so as to meet the conditions (step S1403).

For instance, in the above first example, since it results in a traveltime width set at 10 minutes with a low reliability, the informationprocessor modifies the travel time width to a suitable value (e.g., 20minutes). In the above second example, it results in a travel timeprobability set at 90% with a low reliability, the information processormodifies the travel time probability to a suitable value (e.g., 70%).When the minimum value of the travel time range is 0 or lower as in theabove third example, the information processor changes only the upperlimit value of the travel time range, for example, changes the maximumvalue of the travel time range to a maximum value (e.g., 25 minutes) orsmaller. When the maximum value exceeds a predetermined value, theinformation processor changes only the lower limit value of the traveltime range, for example, changes the travel time range to a minimumvalue (e.g., 550 minutes) or higher. And the information processorperforms the calculating operation of the step S1401 on the basis of thechanged set value, and repeats the operations of the steps S1401 toS1403 until the above conditions are satisfied. However, even afterrepeating the above operations a predetermined number of times, if theprocessor fails to obtain a result satisfying the above conditions, thenthe processor terminates the operation as no solution. And theinformation processor outputs a result last obtained to the display 205(characters or figures) or a loudspeaker (voice) or the like (S1404).

Screen display examples of the display 205 are shown in FIGS. 15A, 15B,and 15C. In FIG. 15A, reference numeral 490 denotes an average traveltime (average required time) or a travel time expected value, numeral493 denotes a travel time range, and 493 denotes a travel timeprobability. In FIG. 15B, reference numeral 496 shows an example whenthe travel time range is displayed only by its upper limit value becausethe minimum value of the travel time range is 0 or lower. In FIG. 15C,numeral 497 shows an example wherein the processor fails to obtain asolution satisfying the above conditions with a result of no solution.In this connection, the values of the travel time range and travel timeprobability may be displayed in the form of a stacked bar chart or a piechart. With it, the user can intuitively know the car status even duringdriving.

Further, information (route information) such as travel times for aplurality of routes may be displayed. In this case, the routeinformation can be displayed to be arranged in an ascending order ofpredetermined route types (e.g., in an order of shortest time route,expressway priority, and public road or non-expressway priority), or inan increasing order of travel time (in a younger order of estimatedarrival time). Or the travel time range or the estimated arrival timerange and the probability thereof may be displayed, and routeinformation may be displayed to be arranged in an increasing order ofthe travel time expected values or in a decreasing order of theprobability. In addition, a specific route and route information may bedisplayed on a map to be overlapped with the map. The embodiment of thepresent invention has been explained above.

In accordance with the present embodiment, even when traffic informationexternally received is not necessarily sufficient in the stabilityquality and information quantity, the system can accurately generatereal-time traffic information, statistical traffic information, andpredicted traffic information including a highly practical travel timerange and a probability thereof, with respect to many links includinglinks to which information is not provided, by statistically processingthe traffic information.

In accordance with the present embodiment, further, since the traveltime range of a route and the probability thereof are displayed, theuser can intuitively know the arrival time width and a frequency thereofand can easily make a trip plan. In this way, there can be provided acar navigation system which has a good convenience of use.

The present invention is not restricted to the above embodiment, but maybe modified in various ways without departing from the spirit and scopethereof. For example, the statistical traffic information DB may bestored in such a storage medium as CD, DVD, memory card or hard disk.When the user terminal 200 displays traffic information, part of thetraffic information already estimated and complemented may be displayedto be distinguished from traffic information not complemented yet, as byusing different display colors for these information.

The car navigation system of the present invention for creating trafficinformation to be used in the car navigation systems includes a trafficinformation acquiring means for externally acquiring traffic informationincluding information about link travel time, and a complementing meansfor calculating traffic information about travel time by performingestimate/complement operation over a non-provision link to whichinformation about travel time is not provided by the traffic informationacquiring means. The complementing means may calculate an average travelspeed of all links or links having the same road attributes as thenon-provision link within a predetermined area in which thenon-provision link is present, regard the calculated average travelspeed as a travel speed of the non-provision link, and calculate atravel time for the non-provision link.

The traffic information providing system may include a storage means forstoring traffic information acquired by the traffic informationacquiring means; a statistical means for statistically processing pasttraffic information stored by the storage means; and a predicting meansfor predicting a travel time of a specific link after passage of apredetermined time with use of the current traffic information acquiredby the traffic information acquiring means, the traffic informationstatically processed by the statistical means, and the trafficinformation calculated by the complementing means.

The car navigation system may include a means, in response to a requestfrom the car navigation system, for molding the traffic informationacquired by the traffic information acquiring means and the trafficinformation calculated by the complementing means to data having apredetermined format, and for transmitting the formatted data to the carnavigation system.

A method for displaying traffic information in accordance with thepresent invention is employed in the traffic information providingsystem for creating traffic information to be used in the car navigationsystem. The method includes a step of externally acquiring trafficinformation including information on a link travel time, and acomplementing step of calculating traffic information on a travel timeby estimating and complementing a non-provision link to which theinformation on the travel time is not provided through the trafficinformation acquiring step.

Another embodiment of the present invention will next explained. FIG. 16shows a general system in accordance with another embodiment of thepresent invention. The system includes a car terminal 1606 mounted on avehicle 1611, a mobile telephone network 1604, an Internet serviceprovider (which will be referred to merely as the provider, hereinafter)1607, a broadcast provider 1605 for receiving data transmitted fromcommunication/broadcast satellite and distributing the receive data tousers via an IP network 1603, a navigation server 1602 for receiving andtransmitting the distributed data from and to the provider 1607, afixed-line telephone network 1608 connected with the provider 1607 forperforming data transfer via the IP network 1603 or the mobile telephonenetwork 1604, and a PC (Personal Computer) 1610 of a personal user. Thenavigation server 1602 is connected with a traffic information center1613 via a private line network 1612.

The car terminal 1606 can obtain information by accessing the navigationserver 1602 via the mobile telephone network 1604. Similarly, the PC1610 can obtain information by accessing the navigation server 1602.

The navigation server 1602 has a route searching engine, mapinformation, site point data such as restaurant and convenient store,traffic information, etc. The navigation server 1602, in response to arequest from the car terminal 1606 or the PC 1610, searches forinformation and returns it thereto. The navigation server having, inparticular, the route search engine, executes route searching operationwhen receiving a route search request from the car terminal 1606 or thePC 1610, returns its result thereto, and also stores the result in thenavigation server 1602. The route searched result stored in thenavigation server 1602 can be again used later. For example, the userissues a route search request from his home PC 1610 beforehand on theprevious day. And when he rides in the car on the next day, he candownload the previously-searched route from the car terminal 1606 anduse it to guide the car.

FIG. 17 shows a detailed structure of the navigation server 1602. Thenavigation server 1602 has a CGI (Common Gateway Interface) 1701, atraffic information server 1702, a guidance server 1703 a map/POI (pointof interest) server 1704, and a customer DB server 1705.

The navigation server 1602 receives longitude/latitude information aboutthe car terminal 1606, moving speed information, moving direction, IDnumber, authentication password, the engine rotational speed of thevehicle 1611, and other parameters indicative of the status of thevehicle 1611, sent via the IP network 1603, as data relating to arequest service. Thereafter, the navigation server authenticates theuser at the CGI 1701. In response to user's request service, thenavigation server sends data to any of the map/POI server 1704, guidanceserver 1703 and traffic information server 1702.

Each of the servers, when receiving the data, performs processingoperation based on the received data, and transmits information aboutthe user's request service to the car terminal 1606 via the CGI 1701, IPnetwork 1603, Internet service provider 1607, and mobile telephonenetwork 1604 (which route will be referred to as the communicationnetwork, hereinafter). Or when the reception of the information aboutthe service becomes more expensive than broadcast, the navigation servertransmits it to the car terminal 1606 via the CGI 1701, IP network 1603,broadcast provider 1605, and communication/broadcast satellite 1631(which route will be referred to as the broadcast network, hereinafter).

Next, the function of each of the above servers will be explained. Thetraffic information server 1702, which processes traffic information, isprovided with a traffic information search engine and a trafficinformation database. The server 1702 is also connected to the trafficinformation center 1613 via the private line network 1612. The trafficinformation server 1702 has a function of receiving traffic informationdistributed from the traffic information center 1613, processing thereceived data or transmitting the processed or not-processed data to thecar terminal 1606.

The traffic information center 1613 has a function of collecting trafficinformation from all parts of Japan, and also a function of distributingtraffic information. Generally speaking, car sensors are installed alonga road at intervals of a certain distance, and the presence or absenceof a congestion on the road is decided depending on the detected statesof the sensors. Or the presence or absence of a congestion may bedecided on the basis of speed information uploaded from a probe car 1707running along the road. Information distributed from the trafficinformation center 1613 include information about congestion,restrictions, parking lot, service area (SA), and parking area (PA). Thetraffic information server 1702 distributes traffic information aboutthe vicinity of the car terminal 1606, or searches for trafficinformation on the route or about the vicinity of the route on the basisof the route searched result, by processing such information. It goeswithout saying that the traffic information server also can searchtraffic information about the vicinity of a desired site point anddistribute it.

The search/guidance server 1703, which calculates route/guidanceinformation, is provided with a route search engine and a map DB forroute searching. After the user authentication of the CGI 1701, on thebasis of departure position information, goal position information,search information and other option data sent from the car terminal1606, the route search engine creates a route coordinate point array andguide point information by referring to information in the routesearching map DB. The searching conditions are information associatedwith route searching conditions of, for example, utilizing expressway asfrequently as possible, using non-expressway or public roads asfrequently as possible, or preferentially finding a route requiring ashortest time. A route to be calculated depends on the searchingconditions.

The searched route result is stored in the customer DB server 1705, and,when the navigation server receives an on-route traffic informationrequest from the car terminal 1606, the information is acquired orreferred to from the traffic information server 1702. This is intendedalso to cope with the situations when a route re-transmission request isissued from the car terminal 1606 or when the route information isdivided into small pieces of data and then distributed little by little.As a result, when the quantity of the searched route data is large, thedata can be divided into small pieces of data and then distributedlittle by little.

The map/POI server 1704 functions to manage display map, POIinformation, etc to be distributed to the car terminal 1606. The serveralso has a function, when the navigation server receives a request fromthe car terminal 1606 to download a POI (point of interest) or a map, ofclipping the POI or map according to the request parameter and returningit to the car terminal. The POI information is used to be set as a goalposition for route searching or to distribute information aboutfacilities in the vicinity of the car. The POI information includesinformation about, e.g., restaurant, convenient store, bank, etc. ThePOI information includes at least the title and latitude/longitude of afacility. The POI information may include, in addition to the aboveinformation, for example, information about telephone number, address,comment character string, photograph, etc for a facility.

The customer DB server 1705 is used to store information on customers.Stored in the server are not only private information about customersbut also an access history from the car terminal 1606 and a searchedroute for each user. The route information includes at least informationabout the route point array and guide point. When route link informationis previously stored, it can be used for extracting traffic informationon the route. The customer DB server 1705 can be used to register a newuser, delete registration, change registered contents, confirmregistered contents, search for charge information of access fee,confirm the charge information, and so on, as services.

The structure of the car terminal 1606 in the present embodiment will beexplained. The car terminal 1606 has a display 1632, a GPS (GlobalPositioning System) receiver 1636, a main body 1637, a memory card slot1634, a portable telephone 1633, a remote controller 1635, and amicrophone 1638. The display 1632 is a device which can display graphicsand which is predominantly of a liquid crystal type. The GPS receiver1636 is a device which receives a position measurement signal andcalculates a coordinate position of the car terminal 1606. Incorporatedin the main body 1637 are a CPU, a memory, a power source, and a unitfor graphics display. The portable telephone 1633 is a device forcommunicating with an external device, that is, for transmitting orreceiving data to or from the aforementioned navigation informationprovider. The remote controller 1635 is used for the user to transmitdesired operation information to the car terminal 1606 using a button orbuttons thereon. If necessary, the user also can transmit a command tothe car terminal by voice using the microphone 1638.

The memory card slot 1634 is used to store data received from thenavigation server 1602 or to load past-downloaded information into thecar terminal 1606, by loading an external memory into the slot 1634. Amemory card to be loaded into the memory card slot 1634 can be usedmerely as a storage or be used to authenticate user information forreceiving communication or broadcast information. For example, when avehicle carrying the car terminal 1606 thereon is such a car as arentacar which can be used by many people, the user can use the serviceby inserting a memory card having authentication information writtentherein into the memory card slot 1634. And if the memory card has anupper limit money amount for the service previously set therein, theuser can use the service within the limit of his estimated expenditure.

When the user previously downloads information about a departureposition and a map in the vicinity thereof into the memory card, he canstore labors from downloading the map from the navigation server 1602 inthe initial state. Further, when the service once used by the user ispreviously written in the memory card, uploaded to the navigation server1602 at constant intervals, and analyzed by the navigation server 1602;information according to his preference can be distributed.

In the aforementioned arrangement, the portable telephone 1633 has beenused as a communication device. However, the portable phone may bereplaced with another communication device, a PDA (Personal DigitalAssistance), or a modem integrally built in the main body 1637. In placeof the portable telephone 1633, an in-car LAN (Local Area Network) maybe connected. In place of the GPS receiver 1636, further, positionidentifying service based on PHS (Personal Handyphone System) may beused.

The aforementioned arrangement is assumed for the car terminal 1606 toreceive data via the communication network. In addition to it, however,a receiver capable of receiving broadcast wave from thecommunication/broadcast satellite, broadcast wave based on terrestrialdigital broadcast, or broadcast wave using FM wave, as well as a devicefor decoding the received data can be attached to the main body 1637.

The aforementioned arrangement is designed to receive and transmit datafrom and to the navigation server 1602 via the communication network.When the arrangement is designed to perform data transfer usingbroadcast media, an interface with an antenna, a decoder, etc arerequired to receive broadcast information.

Explanation will be made as to the structure of a car navigationapplication program (which will be abbreviated merely to the navigationapplication, hereinafter) which operates on the car terminal 1606, byreferring to FIG. 28. The navigation application has, as its functionalmodules, a controller 2801, a car position manager 2802, a trafficinformation manager 2803, a traffic-information request range setter2804, a map manager 2805, and a guide information manager 2806.

The controller 2801 is a module for controlling a flow of the operationof the navigation application. The car position manager 2802 is a modulefor analyzing a signal from the GPS receiver 1636 and managing theposition of the car on the map. In this connection, the signal from theGPS receiver 1636 is not always overlapped with a road on the map. Toavoid this, the car position manager 2802 performs correcting operationby a technique called map matching to cause the car position to belocated on a road of the map.

The traffic information manager 2803 is a module for managing trafficinformation downloaded from the navigation server 1602. The downloadedtraffic information refers to at least traffic information about on aroute or the vicinity of the route or traffic information about thevicinity of a desired point. The traffic information manager 2803manages the type, downloaded time, etc of the downloaded trafficinformation. The traffic information manager 2803 operates cooperativelywith the traffic-information request range setter 2804.

The traffic-information request range setter 2804 is a module, whentraffic information is downloaded from the navigation server 1602, fordetermining a range of information to be downloaded. The rangedetermining method includes a method for the user to enter a range to bedownloaded, a method for the user to select among from conditions set asdefault in the car terminal 1606, and a method for the user to grasp thestatus of resources (such as a available or usable space left in thestorage, and an information transmission capability via the mobiletelephone network 1604) of the car terminal 1606 and decide the range.

The map manager 2805 is a unit for managing map data stored in the carterminal 1606. The manager manages at least the level (detail level) ofthe stored map, range and version.

The guide information manager 2806 is a module for managingroute/guidance information stored in the car terminal 1606. The guideinformation manager 2806 has a main function of managing route/guidanceinformation downloaded from the navigation server 1602. When thenavigation application itself has a route search engine, however, themanager 2806 also can mange route/guidance information output from theroute search engine of the navigation application. Information to bemanaged by the guide information manager 2806 includes at leastinformation about route point array and guide point. In addition, themanager 2806 also can route link information. The guide pointinformation includes at least at least information about guide pointcoordinate and guide direction. In addition, the guide point informationmay includes information about, enlarged intersection map, approach laneand guide point title.

FIG. 18 is an example of a sequence of data communication between thecar terminal 1606 and the navigation server 1602 to obtain trafficinformation on a route. First of all, the car terminal 1606 issues aroute search request to the navigation server 1602 (1801), and receivesroute information (1802). The route information has route point arrayand guide point. The car terminal 1606 next issues a request to thenavigation server 1602 to obtain a detailed map in the vicinity of atarget position (1803) and downloads it (1804). However, this isexecuted only when the car terminal 1606 has no such detailed map aroundthe target position. If such a map is already stored in the memory cardor previously downloaded, then the map downloading is unnecessary.

Next, for the purpose of downloading emergency message information, thecar terminal 1606 issues a caution/warning information request (1805)and downloads the character information (1806). Since the emergencymessage contains information about an act of God, an incident, etc, itis desirable to download the emergency message information faster thanother traffic information and to display it on the car terminal 1606.Finally, the car terminal issues a request to obtain on-route trafficinformation other than the emergency message (1807) and downloads it(1808). Although the requested information is described as the ‘on-routetraffic information’ in FIG. 18, the requested traffic information maycontain traffic information about the position of the car or about thevicinity of a desired point.

Traffic information contains, in addition to congestion or restrictioninformation, character information to inform the user of the emergencymessage. Of course, the traffic information may be collectivelydownloaded regardless of such types or only the emergency message may befirst downloaded as shown in FIG. 18. However, even in the case of thecollective download, when the information contains the emergencymessage, it is desirable to display the emergency messagepreferentially.

FIG. 19 shows a sequence of communication between the car terminal andeach server of the navigation server when on-route traffic informationis downloaded. As mentioned above, the range of traffic information tobe downloaded is not limited to the on-route information, but may betraffic information about the vicinity of the position of the car or thevicinity of a desired point, or about on-route and the position of thecar or the vicinity of a desired point.

The car terminal 1606, when issuing a request about on-route trafficinformation to the navigation server 1602, uploads an user ID and arequest range to the navigation server 1602 (1901). With respect to therange of the traffic information, at least following methods (1) to (6)can be specified therefor.

(1) A range between n-th and m-th sections in a route.

(2) A range on a route through which the car passes after passage of nminutes from the position of the car.

(3) A range on a route between the position of the car and a point n kmahead of the car position.

(4) A range on a non-passage route having a traffic information size ofn bytes or less.

(5) A range corresponding to all the sections of a non-passage route.

(6) A range between two points on a route.

Such a range specifying method may be stored previously in the carterminal 1606, may be specified by the user each time trafficinformation is downloaded. Or only one of the aforementioned methods maybe specified or a plurality of combinations thereof may be specified.

The method (1) is when a section range on a route is specified. In thiscase, the word ‘section’ as used therein refers to at least a distancebetween guide points or any one of divisions of a route divided by aconstant distance. Selection of the above may be specified when theroute link information is downloaded from the car terminal 1606, or maybe previously specified in both of the navigation server 1602 and carterminal 1606. In the method (1), on-route traffic informationcorresponding to the range requested by the car terminal 1606 isdistributed regardless of the position of the car.

The above method (2) is when a time range is specified, and the timerange is calculated according to the type of a road along which the carwill run. The calculation is carried out by changing the car speedaccording to the road type, for example, assuming that the speed is 80km/h on expressway and is 30 km/h on non-expressway or public road. Whena time range of passage of 30 minutes or less from now is uploaded fromthe car terminal, calculation is carried out about traffic informationabout a section from the current position to a point 40 km awaytherefrom on the expressway road and about a section from the currentposition to a point 15 km away therefrom on the non-expressway or publicroad, assuming the above speed requirements. In this case, it isnecessary to transmit information about the position of the car from thecar terminal 1606 to the navigation server 1602. In this connection, thevalue of “30 minutes” in the above may be changed to another value, ormay be changed to a constant stored in the server 1602.

The above method (3) is when a range of distance from the position ofthe car is specified, in which case the position of the car and a value‘n’ are uploaded from the car terminal 1606 and the server 1602 searchesfor on-route traffic information in the range. However, as the value‘n’, a fixed value set in the server 1602 may be employed.

The above method (4) is when the size of information to be received isspecified. In this case, an upper limit data size may be transmittedfrom the car terminal 1606, or the data size may be previouslydetermined by the navigation server 1602. When the method (4) isemployed, it is required to transmit the car position from the carterminal 1606 to the navigation server 1602. When the data size istransmitted from the car terminal 1606, the data size may be determinedby the car terminal 1606, e.g., according to communication speed, theusable memory size of the car terminal 1606, and so on. Or the usablememory size of communication speed of the car terminal 1606 may betransmitted to the navigation server 1602, and the data size may becorrespondingly determined by the navigation server 1602.

The above method (5) is when a range on a route along which the car doesnot run yet, is specified. In this case, it is only required to transmitthe car position from the car terminal 1606 to the navigation server1602. The car position can be expressed in the form of a coordinatepoint, a own car position section, etc. The car position section refersto a section in which the car is currently located. When the carposition is expressed by a coordinate point, the navigation server 1602can convert the coordinated point to a own car position section andprovide traffic information about sections between the car positionsection and the end point of the route. However, the method (5) is notnecessarily required. For example, the method (5) can be madeunnecessary by specifying the section between the car position and theend point of the route in the method (1).

The above method (6) is when a range between any two points on a route.In this case, the range between the two points on the route istransmitted from the car terminal 1606 to the navigation server 1602 toacquire traffic information about the range on the route. As in theabove (5), the two-point range may be expressed by coordinate points, aown car position section or the like.

In ones of the above 6 methods which requires the car position to beuploaded from the car terminal 1606 to the navigation server 1602, thecar position is not always placed on the route due to the accuracy ofthe car terminal 1606. Accordingly, it is required for the car terminal1606 or navigation server 1602 to correct the coordinate point in such amanner that the point is on the route.

Whether to use which of the above parameters can be determined by theuser who enters a selection command on the display screen. The parametersetting screen appears when the user selects a menu on the start screen,the parameters of the methods (1) to (6) are arranged on the screen, andthe user specifies desired one of the parameters by pushing or clickinga corresponding radio button. When a distance from the car positions isspecified, a distance specifying screen appears. On the distancespecifying screen, for example, the user can set a distance range byspecifying a distance for each of expressway and non-expressway roads.

The above parameters have default values on the side of the car terminal1606. For example, for the parameters of the above methods (2), (3), and(4), default values can be previously set when the car is on thenon-expressway or public road and when the car is on the expresswayroad. In the case of parameters of the above method (2), with respect toa range through which the car passes through in ‘n’ minutes, a range forthe expressway road should be longer than a range for the non-expresswayroad. In the case of parameters of the above method (3), it is desirableto set to set a default value for the expressway road to be longer thana default value for the non-expressway road. The same holds true evenfor the method (4).

When receiving a on-route traffic information request from the carterminal 1606 via the CGI 1701, the navigation server 1602 stores user'saccess history in the customer DB server 1705. Thereafter, the trafficinformation server 1702 searches for traffic information in a rangespecified by the car terminal 1606.

More specifically, when the on-route traffic information is required(1901), this means that the car terminal requires route informationabout the user stored in the customer DB server 1705 (1902), and inresponse to it, the navigation server extracts the corresponding routeinformation from the customer DB server 1705 (1903) and requires thetraffic information server 1702 to extract traffic information byspecifying a route and a request range (1904). The traffic informationserver 1702 searches for traffic information matching with the sentroute and request range and sends on-route traffic information to theCGI 1701 as a response (1905). The CGI 1701, when receiving the searchedresult, returns the result to the car terminal 1606 (1906).

In this connection, it is not necessarily required to extract routeinformation from the customer DB server 1705, and in the case of atraffic information request, route information in the form of link canbe uploaded from the car terminal 1606. In other words, upontransmitting route information to the car terminal 1606, when the systemis designed to transmit not only route point array information but alsoroute link information together, the need to store route information inthe customer DB server 1705 can be eliminated and the need for thenavigation server 1602 to extract route information also can be removed.When the car terminal 1606 has a route searching function, the terminalgenerates route link information. Thus the terminal can upload the routelink information to the navigation server 1602. Accordingly, thisfunction can be used even when the search/guidance server 1703 or thecustomer DB server 1705 is not provided.

The operation of the navigation server 1602 for extracting on-routetraffic information will be further explained with use of FIG. 20. FIG.20 is a flowchart for explaining the operation of the trafficinformation server 1702 for extracting on-route traffic information. Thetraffic information server first receives a request (1904) of on-routetraffic information extraction from the CGI 1701 (step 2001). At thistime, since the traffic information server also receives route linkinformation and a traffic information request range together, the serverstores these information in the memory (step 2002).

The traffic information server next searches for map mesh on which theroute is extended and reads traffic information on the map mesh. In thiscase, it is assumed that the traffic information server 1702 receivestraffic information from the traffic information center 1613 at regularintervals, and previously stores the traffic information in the trafficinformation DB of the traffic information server 1702 in the form of afile for each map mesh and each information type. For the name of thefile any title can be used. For easy understanding of the mesh ID andinformation type of the file, however, the mesh ID can be used as thefile name and the information type can be used as the extension. Orinformation from the probe car 1707 may be stored in the trafficinformation DB of the traffic information server 1702 and may be usedfor the above purpose.

Next, the traffic information server 1702 processes all ones of links ofthe sent route which are included in the request range of the trafficinformation (step 2004), and searches for traffic information aboutroute links not processed (step 2005). The searching of trafficinformation can be realized by matching the link ID included in theroute link information with the link ID included in the trafficinformation. After complementing the operation of the step 2005 aboutall route links included in the request range, the traffic informationserver finally collects traffic information for each guidance section(step 2006). The word “guidance section” as used herein refers to a rowof route links between guide points. The collecting operation is notalways necessary. For example, in the case where the car terminal 1606has route link information, even when traffic information for each linkis sent to the car terminal 1606, the collecting operation can becarried out by the car terminal 1606.

When the car terminal has route link information, however, in order toavoid mismatching between link information, the information is requiredto be based on the route searching map DB of the search/guidance server1703. To this end, when route link information is sent from the carterminal 1606 to the navigation server 1602, map format and version maybe sent together with the route link information. That is, thenavigation server 1602 performs the operation when the map format andversion coincide with those of the route searching map DB. When acoincidence is not found, an error code is sent from the navigationserver 1602 to the car terminal 1606 s. Or the route link held in thecar terminal 1606 also may be based on link information based on a VICS(Vehicle Information and Communication System). With it, the navigationserver 1602 and the car terminal 1606 have the same link informationwithout mismatching between links. In this connection, it is desirableto make the version of the link to coincide with the version of the linkof the VICS.

The extracting operation of on-route traffic information as viewed fromthe car terminal 1606 will be further explained by referring to FIG. 21.In a step 2101, first, a range on a route requiring traffic informationis set. This is carried out by accepting a range specified, e.g.,according to the methods (1) to (6).

The car terminal 1606 next confirms whether or not route linkinformation is present in the car terminal (step 2102). When route linkinformation is present in its own terminal, the car terminal transmitsthe route link information to the navigation server 1602 together with arequest range upon transmitting a traffic information request thereto(step 2104). When route link information is absent in its own terminal,the terminal transmits only the request range to the navigation server1602 (step 2103).

After issuing the request to the navigation server 1602, the carterminal waits for completion of the operation of the navigation server1602. When the operation of the navigation server 1602 is completed andthe car terminal 1606 receives a response from the navigation server1602, the terminal downloads traffic information from the navigationserver 1602 (step 2105). After the terminal successfully downloadstraffic information, the terminal displays the received trafficinformation on the display 1632 (step 2107). If the downloading of thetraffic information ends in a failure for some reasons, the terminaldisplays an error message on the display (step 2108).

The screen transition for the downloading of traffic information will befurther explained with use of FIGS. 22, 23A, and 23B. As shown in FIG.22, a car position 2201 and a route 2202 are displayed on the screen.Under this condition, when the user operates the remote controller 1635or clicks any of buttons in the screen, a menu appears. A main menu 2211is displayed in the lower part of the screen of FIG. 22. The main menu2211 is made up of a traffic information menu 2214, a map acquisitionmenu 2215, and a route search menu 2216. When each menu is selected, asubmenu further appears. In the case of FIG. 22, the traffic informationmenu 2214 is selected from the main menu 2211, so that a ‘on-route’submenu 2212 and a ‘current position vicinity’ submenu 2213 aredisplayed. When the user selects the ‘on-route’ submenu 2212 from thetraffic information menu 2214, this causes the terminal to startdownloading on-route traffic information.

When the user selects the 2212, the car terminal 1606 is connected tothe navigation server 1602 to download on-route traffic information.Before the terminal receives on-route traffic information back from thenavigation server 1602, the display of all the menus once disappears anda message saying “acquiring traffic information” appears as overlappedwith the map. In this connection, it is also possible not to display themap and to display only the message. When the connection of the terminalwith the navigation server ends in a failure for some reasons, a messagesaying “server connection failed” appears.

When the connection with the navigation server is successful, thenavigation server 1602 extracts on-route traffic information. Whenreceiving the on-route traffic information from the navigation server1602, the car terminal 1606 displays the received traffic information onthe screen. Before the car terminal car terminal 1606 displays thereceived traffic information, the terminal confirms the presence orabsence of emergency information in the downloaded traffic information.In the case of the presence, the terminal displays the emergencyinformation. FIG. 23A displays the emergency message and FIG. 23Bdisplays traffic information other than the emergency message. Whenemergency information is included in the downloaded traffic information,the screen of the FIG. 23A appears, showing an emergency message 2301.

After the emergency information is displayed, if the terminal detectsthat the remote controller 1635 was operated or a confirm button (notshown) given in one side of the screen was clicked by the user, thencongestion information 2302 and 2303 other than the emergencyinformation appear as shown ins FIG. 23B. In this case, when the display1632 of the car terminal 1606 is equipped with a touch panel, theconfirm button can be provided on the screen. Or even in the case wherethe confirm button is not clicked, when a predetermined timeout set timeelapses after the display of the emergency information and the terminaldetects the timeout, the terminal erases the emergency message 2301 anddisplays other traffic information (e.g., the congestion information2302 and 2303 other than the emergency information). In this connection,the switching of the display from the emergency information to otherinformation due to the timeout may be carried out in an arbitrarymanner, and the emergency information may be continuously displayeduntil the user clicks the confirm button. In the absence of theemergency information, after the car terminal downloads trafficinformation, the terminal displays traffic information other than theemergency information. This operation is intended to preferentiallydisplay the emergency information to be notified first to the user. Forexample, when a traffic suspension takes place on a road along which thevehicle 1611 now proceeds due to an accident or calamity, the trafficsuspension information should be informed preferentially to the user toother congestion restriction information, etc. Such information as tohave a high emergency is preferentially displayed.

In a method for extracting information having a high emergency from thetraffic information downloaded by the car terminal 1606, for example,attribute information indicative of emergency information is previouslyattached in the navigation server 1602 and only information having suchan emergency information attribute is regarded as emergency information.Or even information having no emergency information attribute can bedetermined as emergency information by the car terminal 1606. Forexample, when an accident or calamity occurs and the driver of the carcan judge it as dangerous, even information having no emergencyinformation attribute in the navigation server 1602 can bepreferentially displayed by the car terminal 1606.

Although the congestion information 2302 and 2303 are displayed asshifted slightly from the route 2202 in the present embodiment, thecongestion information and the route may be differently colored and thecongestion information may be displayed to be overlapped with the route.

Further, the emergency message 2301 is displayed and thereafter thecongestion information 2302 and 2303 are displayed in the presentembodiment. However, the present invention is not limited to the displayin the above order, but these traffic information may be simultaneouslydisplayed, the system may wait for the clicking of the confirm button orfor a timeout, after which the congestion information 2302 and 2303 canbe left and the emergency message 2301 can be erased.

The downloading of the on-route traffic information is not restricted tothe case where the user selects the on-route traffic-informationdownload menu and downloads explicitly. When the car terminal 1606 hasroute information and the user wants to download traffic informationabout the vicinity of the current position of the car, the user candownload traffic information together with on-route traffic information.This is intended to mismatching between the traffic information aboutthe vicinity of the current car position and the on-route trafficinformation. Even in this case, however, a range of the on-route trafficinformation to be acquired is set, and the setting is carried out in thesame manner as in the aforementioned embodiment.

FIG. 24 is a sequence chart when traffic information about the vicinityof the position of the car is downloaded. The car terminal 1606 firsttransmits a request of traffic information about the vicinity of the carposition together with the car position to the CGI 1701 (2401), and theCGI 1701 in turn requests the traffic information server 1702 to sendthe traffic information about the vicinity of the car position (2402).The traffic information server 1702 extracts the requested trafficinformation and returns the extracted information to the CGI 1701(2403). The CGI 1701 then returns the received information to the carterminal 1606 (2404).

Subsequently, the car terminal 1606 transmits a on-route trafficinformation request to the navigation server 1602 (1906). The subsequentoperations are as already explained in connection with FIG. 19. In thisway, when the car terminal 1606 downloads traffic information about thevicinity of the car position, as soon as the car terminal accepts thecar position vicinity information from the CGI, the terminalautomatically transmits an on-route traffic information request to theCGI to acquire traffic information about a section of the route throughwhich the car does not pass yet. In the above operations, the terminalrequests the car position vicinity traffic information and the on-routetraffic information separately from the navigation server 1602. However,Such two types of requests may be first requested, and the car positionvicinity traffic information and the on-route traffic information may beseparated received from the CGI. Further, the CGI may respond to the carterminal by collecting the two types of traffic information into asingle piece of information.

How to acquire traffic information about the vicinity of the currentposition of the car will be further explained by referring to FIG. 25.FIG. 25 is an example of a display screen when traffic information aboutthe vicinity of the current car position.

In response to user's operation of the remote controller 1635 or touser's clicking of a button provided in the periphery of the screen thecar terminal 1606 displays a menu similarly to FIG. 22. When nowdetecting the selection of the ‘current position vicinity’ submenu 2213,the car terminal 1606 is connected to the navigation server 1602 and putin a traffic information wait state. After the car terminal 1606 isconnected to the navigation server 1602, downloads traffic informationtherefrom, and then completes the downloading of the trafficinformation; the screen is transited to the screen of FIG. 25 to displaythe acquired traffic information 2501 and 2502. The traffic information2501 is now data (not traffic information about the on-route 2202)downloaded as the traffic information about the current car position.The traffic information 2502, on the other hand, is data downloaded ason-route traffic information. If there is an emergency message in thedownloaded data, then the car terminal preferentially displays theemergency message, similarly to the case of acquiring the on-routetraffic information.

The display of the emergency message is not limited to only when trafficinformation is downloaded. When the car terminal 1606 accesses thenavigation server 1602, the terminal desirably necessarily downloads theemergency message, because the emergency message should be informed tothe user as soon as possible, which will be explained by referring toFIG. 27.

FIG. 26 is a sequence after the car terminal 1606 requires thenavigation server 1602 to transmit map information to the terminal untilthe terminal downloads an emergency message on a route. The car terminal1606 issues a request for map information to the navigation server 1602(2601), and the request is accepted by the CGI 1701. The CGI 1701requires the map/POI server 1704 to send a map of a site specified bythe car terminal 1606 thereto (2602), and accepts the map information ofthe specified request position therefrom (2603). When accepting the map,the CGI 1701 transmits the map information to the car terminal 1606(2604).

After acquiring the desired most preferentially, the car terminal 1606issues a request having an emergency message information user IDattached thereto to the navigation server 1602 (2605). How to acquire anemergency message on a route has substantially the same sequence as howto acquire on-route traffic information. More specifically, the CGI 1701requires the customer DB server 1705 to send route information with useof a user ID specified (2606), and acquires the route information of thecorresponding user (2607). Next, the CGI 1701 transmits the acceptedroute information to the traffic information server 1702 (2608), thetraffic information server 1702 in turn searches for an emergencymessage, and the CGI 1701 receives the searched result from the trafficinformation server (2609) and transmits it to the car terminal 1606(2610).

If the car terminal 1606 has route link information relating to its ownguide route, then the terminal may upload the link information to thenavigation server 1602 in such a manner that the navigation serversearches for an on-route emergency message with use of the linkinformation as a key. When the car terminal 1606 requires an emergencymessage, the car terminal can inform the navigation server 1602 of therange on the route so far explained above. In other words, the terminalcan download only an emergency message present in the range.

Although the most preferentially and the emergency message areseparately requested and received in the present embodiment, these maybe simultaneously requested and received together. That is, whenaccepting a map information request, the navigation server 1602 may nottransmit only the map information first to the car terminal 1606, butmay search for an emergency message on the route and transmit theemergency message to the car terminal 1606 together with the mapinformation. This is not limited to when the map information isrequired, and can be implemented even when information such as POI otherthan the map is requested.

The above will be further explained by referring to a screen example.The car terminal 1606 displays the main menu 2211 similar to FIG. 22according to user's operation of the remote controller 1635 or user'sclicking of a button provided in the periphery of the display screen.When the user selects the map acquisition menu 2215, a target pointvicinity menu for acquiring a map in the vicinity of a target point anda current point vicinity menu for acquiring a map in the vicinity of thecurrent point further appear. And when the user selects the target pointvicinity menu from the map acquisition menu 2215, that is, when the userinstructs the car terminal 1606 to acquire the map in the vicinity ofthe target point, the car terminal is connected to the navigation server1602. After the car terminal 1606 is successfully connected to thenavigation server 1602, the terminal transmits a map request to the CGIto acquire map information. Next, the car terminal requests thenavigation server 1602 to send an on-route emergency message. In thepresence of such an emergency message, the car terminal downloads it.

After all information have been downloaded, the map information and theemergency message are displayed, which is shown in a display screen ofFIG. 27. In FIG. 27, an emergency message 2701 is displayed, and a mapin the vicinity of the specified target position is also displayed.Center lines 2702 and 1703 are plotted when the displayed map is a siteother than the current position. The map is displayed so that anintersection point between the center lines corresponds to the targetposition, and a mark indicative of the target position is also plotted.

In FIG. 27, the emergency message 2701 and map information are displayedsimultaneously. However, it is also possible to display the emergencymessage 2701 first and then to display the map information in thevicinity of the target position. With this screen, however, the useraccessed the navigation server 1602 for the purpose of acquiring the mapinformation. Thus, when the user preferentially displays informationother than user's target position, it is desirable to display the effecton the screen of the car terminal 1606.

When the user operates the remote controller 1635 or clicks the confirmbutton in the periphery of the screen during display of the screen ofFIG. 27, the emergency message 2701 disappears and the screen display istransited to a screen showing a map in the vicinity of the target point.In the absence of the emergency message, no emergency message cannot bedisplayed and therefore the screen is transited directly to a screenshowing the map in the vicinity of the target point.

It should be further understood by those skilled in the art thatalthough the foregoing description has been made on embodiments of theinvention, the invention is not limited thereto and various changes andmodifications may be made without departing from the spirit of theinvention and the scope of the appended claims.

1. A car navigation system for receiving information provided by atraffic information providing system, wherein the traffic informationproviding system comprises: travel information acquiring means forexternally acquiring traffic information including information about atravel time of each of links making up a road on a map; storage meansfor storing the traffic information acquired by the traffic informationacquiring means; link travel-time probability calculating means forcalculating a probability distribution of travel times of the links withuse of a past traffic information stored by the storage means; routetravel-time probability calculating means for calculating a probabilitydistribution of travel times of a specific route making up a pluralityof links with use of the probability distribution calculated by the linktravel-time probability calculating means; setting means for setting atravel time range or a travel time probability for the specific route;and when the travel time range of the specific route is set by thesetting means, reliability calculating means for calculating aprobability that the travel time of the specific route is in the traveltime range set by the setting means with use of the probabilitydistribution of travel times of the specific route and, when the traveltime probability of the specific route is set by the setting means, forcalculating a travel time range in which the travel time of the specificroute falls in the travel time probability set by the setting means withuse of the probability distribution of travel times of the specificroute; wherein the car navigation system comprises: means for acquiringinformation about the probability that the travel time of the specificroute is in the travel time range set by the setting means or the traveltime range in which the travel time of the specific route falls in thetravel time probability set by the setting means; and means fordisplaying the acquired information about the probability that thetravel time of the specific route is in the travel time range or thetravel time range in which the travel time of the specific route fallsin the travel time probability.
 2. The car navigation system as setforth in claim 1, comprising a changing means, when the resultcalculated by the reliability calculating means fails to satisfypredetermined conditions, for changing the travel time range or thetravel time probability set by the setting means, and wherein thereliability calculating means has means for regarding the travel timerange or the travel time probability changed by the changing means ashaving set by the setting means and for again performing thecalculation.
 3. The car navigation system as set forth in claim 1,comprising means, when displaying traffic information about a pluralityof the specific routes, for displaying the traffic information in anincreasing order of the route travel times or in a decreasing order ofthe probabilities for the travel time.
 4. The car navigation system asset forth in claim 2, wherein said predetermined conditions comprise themaximum width of travel time width or the lower limit valve of traveltime probability, when the calculated probability for the travel timerange of the specific route set by the setting means lowers than thelower limit value of the travel time probability; said changing meanssets said lower limit value of the travel time probability, sets saidlower limit value of the travel time probability as the travel timeprobability, and when the travel time range for the travel timeprobability of the specific route set by the setting means extendsbeyond the travel time width, said changing means sets the upper limitor lower limit of the travel time width as the travel time range.